Photonic crystals with nanocellulose

Nano Crystalline Cellulose (NCC) can be easily extracted from wood. This has been known for several decades (see for modern extraction method the reference 1). It was also demonstrated for decades that letting the dispersion to self-evaporate in a Petri dish produces colourful solid disks (2). The colors were seen to depend on parameters like for instance the pH, initial concentration, and the ionic strength (3). These beautiful patterns were long attributed to NCC self-organizing into a helicoidal liquid crystal (4). In that model, NCC were perfect straight rods well parallel aligned in horizontal uniform layers, each layer slightly rotated compared to the next one (5). This model is too perfect to be real. In fact, the NCC are not rods but rough fibrils, with a net tendency to bundle. Nonobstant, a liquid crystal is really formed. This is demonstrated by microscopic images and laser diffraction patterns. We have identified the liquid crystal as a smectic-like one. However, the series of reactions leading from fibrils to smectic-like, and from smectic-like to color is quite subtle. This is a new model, the smectic-like liquid crystal. This is the results a 3 year fundamental scientific investigation. It is a modern revision to a 50 years old liquid crystal model, the helicoidal model. Prospectives from this realistic model will be discussed. (1) Samir, M.A.S.A.; Alloin, F. ; Dufresne, A. Biomacromolecules 2005 6, 612. (2) Werbowyj, R.S.; Gray D.G. 1976 Mol. Cryst. Liq. Cryst. Lett., 34, 97. ; G. Picard,† D. Simon, † Y. Kadiri,† J.D. Lebreux,‡ and F. Gozayel‡, NSTI 2010,poster session. (3) Dong, X.M.; Gray, D.G. Langmuir 1997, 13, 2404. (4) Giraud-Guille, M.M. Current Opinions in Solid State & Materials Science 1998, 3:221-227 (5) Rita S.; Gray, D.G. Macromolecules 1984,17, 1512.